The present invention relates to a flexible board connector for electrically connecting a flexible board to a circuit board to each other, and to a connection structure between a circuit board and a flexible board.
In recent years, electronic equipment such as portable telephones and video cameras has been increasingly miniaturized, while having a multiplicity of electronic components incorporated inside. In most of these electronic components, leads or terminals are electrically connected to component mounting lands disposed on a circuit board by means of solder. In each of miniaturized portable telephones, a plurality of circuit boards are normally used. On those circuit boards, relatively large component parts such as a liquid crystal display module and a keypad are disposed. Then, flexible boards are widely used for electrical connection between the circuit boards or between the circuit boards and other component parts.
Conventionally, the following connectors or the like are used for the connection of flexible boards to circuit boards.
(1) As shown in FIG. 5, a terminal portion 57 of a flexible board 56 is inserted into a connector 53 as shown by arrow D. The connector 53 has a swing portion 52 that is placed on a circuit board 51 and swings as shown by arrow C. The terminal portion 57 is fixed by the swing portion 52.
(2) As shown in FIG. 6, a connector 63 is placed on a circuit board 61 and has a contact 62 and an engagement claw. A flexible board 66 has an engagement hole for engaging with the engagement claw, and a signal input/output terminal 65. The flexible board 66 is engaged with the connector 63, as shown by arrow E, so that the signal input/output terminal 65 is brought into contact with the contact 62 to obtain conduction (see JP H09-22760A).
(3) As shown in FIG. 7, a flexible board 72 is placed on a surface of a circuit board 71 as shown by arrow F. Then, the flexible board 72 is sandwiched as shown in arrow G by a holding member 74 which covers a portion of the flexible board 72 to be fitted to the circuit board 71. As a result, a protrusion 76, which is provided within the holding member 74 and connected to a plate spring 75, presses a signal terminal 78 provided on a rear surface of the flexible board 72 against a signal terminal 79 provided on a top surface of the circuit board 71, and thus electrical conduction is obtained (see JP H09-69678A).
For electronic equipment that has been increasingly miniaturized, the reduction of its thickness is regarded as important in particular. Under the situation that electronic components or the like are directed toward downsizing and thinning, connectors for the flexible boards are also desired for downsizing and thinning.
However, in the case with use of such a connector 53, 63 as stated above in (1) and (2), the connector 53, 63 is placed on a circuit board 51, 61. Thereby, the connectors 53, 63 are entirely protruded from the top surface of the circuit board 51, 61. This disadvantageously makes it hard to miniaturize the circuit board 51, 61 and the flexible board 56, 66 which are connected to each other. For reduction in thickness of the connector 53, 63, it is conceivable to decrease the thickness of components in the connector 53, 63, such as insulators, terminals or the like. However, this disadvantageously incurs decreases in structural strength, connection failures and the like.
As to the connector 63 in (2), since the circuit board 61 and the flexible board 66 are connected to each other by engaging the engagement claw with the engagement hole, connection strength is relatively weak.
Meanwhile, when the circuit board 71 and the flexible board 72 are connected to each other without using any connector as in the case of (3), the holding member 74 is poor in versatility. This causes increase of cost. Further, the holding member 74 covers a much larger portion of the flexible board 72 in area than the portion where the signal terminal 78 is formed. Also, the holding member 74 has the plate spring 75 and the protrusion 76 in its inside. Moreover the holding member 74 is placed so as to protrude onto the circuit board 71. As a result, these make it difficult to downsize the components.